A conventional semiconductor device used in a flat panel display as a driver IC will be described below taking, as an example, a semiconductor device driving a PDP, which is attracting much attention as a thin high-definition display panel with a large screen.
The PDP comprises a plurality of discharge cells arranged in a matrix, as pixels. The PDP comprising the discharge cells as the pixels displays images utilizing the emission and non-emission of light during discharge from the discharge cells. In a general AC PDP, the plurality of discharge cells (pixels), arranged in a matrix, are composed of a plurality of scan sustain electrodes and a plurality of data electrodes arranged in a direction orthogonal to the scan sustain electrodes. Each of the scan sustain electrodes is made of a scan electrode and a sustain electrode which are arranged adjacent to each other. The scan electrodes and sustain electrodes constituting the plurality of scan sustain electrodes are alternately arranged adjacent to one another.
The semiconductor device used in the AC PDP as a driver IC is mounted on a wiring board and serves as a driver module. The semiconductor device, serving as the driver module, is connected to panel driving electrodes. The semiconductor device connected to the panel driving electrodes allows the PDP to perform an image display operation described below.
The PDP first performs a reset operation to initialize all the discharge cells to the same state. The PDP then applies a scan pulse to the scan electrodes, and in synchronism with the application of the scan pulse, applies a load driving signal that is a data signal for a display state or a non-display state, to the data electrodes. Wall charges are accumulated in the discharge cells for which the display state is selected by the load driving signal.
After applying the scan pulse to the scan electrodes and applying the load driving signal to the data electrodes for all the scan electrodes, the PDP applies a sustain pulse to the scan electrodes and the sustain electrodes so as to alternate voltage polarities. As a result, in discharge cells in which wall charges have been accumulated, the sustain pulse voltage is superimposed onto the wall charges, so that the resulting voltage exceeds a discharge threshold. This causes discharge cells for which the display state is selected by the load driving signal to emit light. In discharge cells for which the non-display state is selected by the load driving signal, the voltage does not exceed the discharge threshold. Consequently, these discharge cells do not emit light. Thus, the display on the entire screen is achieved by the light emission and non-emission of the discharge cells.
The PDP repeats the above operation to display images.
With the increased size of the panel screen and the increased definition and luminance of the panel, in recent years, the semiconductor device used in the flat panel display as a driver IC has needed to deal with multi-pin outputs, high voltage driving, and an improved driving ability.
The improved driving ability and the multi-pun outputs increase driving loads on the semiconductor device and thus the amount of heat generated by the semiconductor device during operation. To solve this problem, a semiconductor device has been proposed in which a flip chip mounted on a wiring board is protected by a peripheral wall surrounding the flip chip and in which an electrically and thermally conductive member is contacted with the flip chip through an opening in the peripheral wall, with a chassis connected to the wiring board with the flip chip mounted thereon (Japanese Patent Laid-Open No. 2003-115568). This configuration can improve heat dissipation. Moreover, a ground potential can be enhanced by setting the chassis connected to the wiring board with the flip chip mounted thereon, at the ground potential.
Further, with the improved driving ability and the multi-pin outputs, the increased length of the flip chip associated with the multi-pin outputs disadvantageously increases the length of power supply wiring inside the flip chip and thus impedance. Furthermore, voltage disadvantageously drops at the longitudinally opposite ends of the inside of the flip chip. To solve this problem, the conventional semiconductor device needs to ensure an appropriate wiring width to reduce wiring resistance and thus needs to increase chip size. Moreover, it is necessary to use an expensive multilayer wiring board instead of the conventional inexpensive single layer wiring board.
However, since the panel with the larger screen uses several to several tens of driver ICs, the increase in chip size and the multiple layers in the wiring board significantly increase costs. Further, when the flip chip is mounted on the multilayer wiring board, heat dissipation efficiency may decrease compared to that in the prior art.